DIFFERENTIATING METHANE SOURCE AREAS IN ARCTIC ENVIRONMENTS WITH MULTITEMPORAL ERS-1 SAR DATA

An assessment using ERS-1 SAR data to differentiate methane source (we tland) and nonsource (nonwetland) areas was undertaken based on radar backscatter modeling and empirical observations of 24 scenes collected over Barrow, AK, in 1991 and 1992. Differences in backscatter between source and nonsource areas were dependent on surface hydrology and ai r temperature, Differential freezing of surface materials on daily to seasonal time scales greatly enhanced the separability of wetlands and nonwetlands with ERS-1 SAR. Radar return for nonwetlands decreased dr amatically whereas backscatter from wetlands decreased little when fre ezing air temperatures coincided with the SAR overpass. Maximum separa bility between wetlands and nonwetlands, as determined from observed a nd modeled radar backscatter, were the result of changes in the dielec tric constant of the plant and surface materials with phase change dur ing freezing. This study has indicated the need to consider air temper ature at the time of acquisition in selecting ERS-1 SAR scenes for dif ferentiating methane source and nonsource areas.